The subject matter disclosed herein relates to turbomachines. More specifically, the present disclosure concerns improvements in sealing arrangements for turbomachines working at high temperatures.
Turbomachines, such as centrifugal compressors, turbines, and the like, are often operated at high temperature, and both the rotor components as well as the stator components thereof are subject to thermal expansions.
In fast start-up machines, i.e. machines where the start-up procedure is performed in a short period of time, the seal clearance between a sealing arrangement, mounted on a stationary component, and a rotary component must be designed so that during start-up the sealing arrangement does not contact the rotary component, which is subject to a fast dimensional increase due to centrifugal and thermal radial growth in radial direction.
In order to prevent sealing damages during start-up, due to the stator radial growth being slower than the rotor radial growth, the diameter dimension of the sealing arrangement is designed so that a sufficient radial clearance is maintained also at start-up. Consequently, the radial sealing clearance, when the steady state operating condition of the turbomachine is achieved, is comparatively large. A large radial clearance causes a drop of efficiency of the turbomachine.
There is therefore a need for an improved control over the radial clearance of sealing arrangements in turbomachines working at high temperature and having a fast start-up procedure.